Traditional wooden boats are constructed by carefully assembling a wood frame and covering the framing with wood decking (“strakes”). Each strake is fabricated and installed by hand. Tight fitting joinery is necessary for structural, water tightness and cosmetic reasons. To achieve tight joinery, pieces need to be custom fit by highly skilled labor. Because of the cost of skilled labor and the amount of time necessary for the hand fitting of the components, wooden boats have been much more expensive to make than have composite boats.
Composite boats are constructed of multiple layers of a structural reinforcement fabric such as fiberglass, Kevlar or carbon fiber, a core material such as urethane or polystyrene foam for structural reinforcement and floatation, a resin/adhesive such as epoxy, vinyl ester or polyester. (“Kevlar” is DuPont's trademark for a polyamide fiber). The resin both binds the reinforcements together while acting as a filler for the weave of the fabric. Gunwales are added along the upper edges of the composite hull.
Contemporary composite canoes are manufactured in two basic ways: the “wet-out” method and the vacuum infusion method. The former method involves placing multiple layers of reinforcement into a female mold and then thoroughly wetting those layers with resin applied by hand. The results of this method result in a heavy boat due to the large amount of resin used. The “wet-out” technique is labor intensive and exposes the builders to health risks associated with working resins and their associated solvents.
With the second method—vacuum infusion—reinforcing elements are placed in a mold, then are covered with an infusion media, release fabric and airtight film, and finally are placed under a vacuum via a plastic tubing plumbing system. The air between the mold and film is extracted while the force of the vacuum draws in the resin. The resulting boat is lighter than a wet-out boat because the vacuum consolidates the reinforcements and draws out excess epoxy. In addition, the vacuum infusion method greatly reduces the builder's exposure to the epoxy and its solvents. A disadvantage of current infusion techniques is that they require the use of vacuum media (plastic mesh or core material) to allow the air/epoxy to flow across the fabric reinforcement and they also require substantial amounts of plastic tubing to create the air/epoxy distribution system. The infusion materials are consumed by the production of each boat, as they are either stripped from the finished hull and thrown away, or are left buried within the hull.
Canoes built using fiberglass are normally constructed using five or six layers of reinforcement and cored ribs layered with additional layers of fiberglass. The multiple layers and ribs are necessary to create an adequate structure. Gunwales and two or three thwarts (cross-members) are required as part of the basic structure. These layers are held together using approximately 3.5 to 4 gallons (7-8 liters) of resin. The final result is boat that typically weighs around sixty five to seventy five pounds (30-35 kg), has a fairly brittle hull, and requires additional means of floatation to prevent it from sinking when swamped.
Canoes built using carbon fiber or Kevlar normally have two or three layers of reinforcement and cored ribs layered with additional layers of carbon or Kevlar. Owing to the higher strength of carbon/Kevlar, these boats use fewer layers of reinforcement and therefore less resin to achieve the required minimum strength. This results in a finished boat that typically weighs 40 to 45 pounds (18-20 kg) or about 40% less than a fiberglass boat. However, the cost of carbon/Kevlar is approximately eight to ten times that of fiberglass, making boats of this type substantially more costly than those of fiberglass.